Benitez was equally upset at the lack of transfer activity, repeatedly stating he had "no idea" if anyone was close to joining the club or not.
There appears to be a marked disconnect between Benitez and club owner Mike Ashley as the Spaniard doubts whether his recruitment requests will be met ahead of the transfer window deadline.
Less than 24 hours after manager Rafa Benitez had said "things are not going well off the pitch and you can see a reflection of that on the pitch" in the wake of a 4-0 friendly defeat to Braga, the Magpies have acted by bringing in Muto. "I am really looking forward to playing in front of the fans".
With the transfer deadline just six days away and his contract approaching its previous year, Benítez aired his concern about the current situation and admitted he was fearful about the oncoming season: "The fans have to be concerned, we are concerned".
Manchester City chase visa for Douglas Luiz amid transfer frustration
I saw three games [of Chelsea] in pre-season and he got it. "I think it will be a good game, always Chelsea is a big rival". "We talked only about 'can I arrive on Monday instead of Sunday?'" "We can try to reduce the gap in the future with work".
With the paperwork now completed, Newcastle fans have been quick to welcome the striker to the club, where he effectively replaces Aleksandr Mitrovic, who was recently sold to Fulham for around £22 million.
The club confirmed on Wednesday that the process has been completed, meaning he becomes their fifth signing of the transfer window, following Martin Dubravka, Ki Sung-yueng and Fabian Schar and the loan deal for Kenedy.
You've got to feel sorry for Rafa Benitez.
Information from The Associated Press and Reuters was used in this report.
With Florian Lejeune out for most of the season with a ruptured cruciate ligament and Mbemba now at Porto, retaining Lascelles is a priority. "But I can't say too much".